1. Field of the Invention
This invention relates to downhole drilling, and more particularly to apparatus and methods for retaining and tensioning transmission lines in downhole tools.
2. Description of the Related Art
For half a century, the oil and gas industry has sought to develop downhole telemetry systems that enable high-definition formation evaluation and borehole navigation while drilling in real time. The ability to transmit large amounts of sub-surface data to the surface has the potential to significantly decrease drilling costs by enabling operators to more accurately direct the drill string to hydrocarbon deposits. Such information may also improve safety and reduce the environmental impacts of drilling. This technology may also be desirable to take advantage of numerous advances in the design of tools and techniques for oil and gas exploration, and may be used to provide real-time access to data such as temperature, pressure, inclination, salinity, and the like, while drilling.
In order to transmit data at high speeds along a drill string, various approaches have been attempted or suggested. One approach that is currently being implemented and achieving commercial success is to incorporate data transmission lines, or wires, into drill string components. These data transmission lines bi-directionally transmit data along the drill string. In certain cases, drill string components may be modified to include high-speed, high-strength data cable running through their central bores. In certain cases, this approach may require placing repeaters or amplifiers at selected intervals along the drill string to amplify or boost the signal as it travels along the transmission lines.
In order to implement a “wired” drill string, apparatus and methods are needed to route transmission lines or wires, such as coaxial cable, along or through the central bore of drill string components. Ideally, such apparatus and methods would be able to retain the transmission lines under tension. This will minimize movement of the transmission line within the central bore and minimize interference with tools or debris moving therethrough. Further needed are apparatus and methods to seal and isolate the transmission lines from drilling fluids passing through the central bore of the drill string. Yet further needed are apparatus and methods to quickly install the transmission lines in downhole tools, while minimizing the need for expensive equipment or highly trained personnel.